•K+ addition to electrolyte significantly improves the morphology and cycleability of Li metal anode.•A modified SHES mechanism called “SHES–K mechanism” is proposed.•The effects of K+ addition to electrolyte could be well explained using SHES–K mechanism.The effects of adding potassium ion (K+) to lithium oxalyldifluroborate (LiODFB)/ethylene carbonate (EC) + dimethyl carbonate (DMC) (1:1 vol.%) electrolyte on the cycle behaviors of lithium deposition–stripping on a Li22Sn5 substrate electrode are investigated. The functions and mechanism of K+ addition to the electrolyte are evaluated through scanning electron microscopy (SEM), inductively coupled plasma-atomic emission spectrometry (ICP–AES), element mapping, energy dispersive spectrometer (EDS), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) analyses. The addition of K+ to the electrolyte significantly improves the morphology of the lithium deposits and the cycleability of lithium deposition–stripping. K+ is not reduced nor incorporated on the substrate during lithium deposition. Based on the reported “self-healing electrostatic shield” (SHES) mechanism, this study proposes the SHES–kinetics mechanism, which considers both kinetic and thermodynamic factors.The addition of potassium ion to the electrolyte significantly improves the morphology of the lithium deposits and the cycleability of lithium deposition–stripping. To explain these effects, we proposed the “self-healing electrostatic shield–kinetics mechanism,” which considers both kinetic and thermodynamic factors.

A Li22Sn5 alloy was prepared as a novel substrate of the metallic Li anode of rechargeable Li batteries for Li+ deposition. The performance of this alloy substrate was compared with those of Li, Cu, and Sn substrates. The deposition–stripping cycling performance of Li on the substrates was studied through the galvanostatic charge–discharge method and cyclic voltammetry. The morphologies of the substrates before and after Li+ deposition were investigated through scanning electron microscopy and digital video microscopy. The electrochemical kinetics of Li+ electrodeposition on the different substrates was studied through the galvanostatic pulse method and linear sweep voltammetry. The solid electrolyte interface films of Li deposits on the substrates were characterized through electrochemical impedance spectroscopy. Results show that Li22Sn5 is an excellent substrate for metallic Li electrodes. “The competitive kinetics model” was proposed as a novel mechanistic model to explain the electrodeposition behavior of Li+ on general substrates based on electrochemical kinetic principles.

A simple polymer pyrolysis method for the synthesis of hierarchically nanostructured NiFe2O4/C composites is reported in this study. The characteristics of the material are examined by thermogravimetry, X-ray diffraction and scanning electron microscopy. The electrochemical performances of the nanomaterial composites are investigated in detail. The results show that the obtained composite retains a high specific capacity of 780 mAh g−1 even after 40 cycles at a current density of 1/8C, and the coulombic efficiency approaches 99%. The reversible specific capacity can still be as high as 200 mAh g−1, at high rate of 4C. The nanostructured NiFe2O4/C composite is a potential competitive anode for lithium-ion batteries.Highlights► A nanostructured NiFe2O4/C is synthesized via the polymer pyrolysis method for lithium-ion batteries. ► The size range of the as-synthesized particles is approximately 50–100 nm. ► The obtained sample retains about 780 mAh g−1 after 40 cycles. ► The reversible capacity is over 200 mAh g−1 at the high rate of 4C.

Sn-doped Li3V2−xSnx(PO4)3/C (x = 0, 0.02, 0.04, 0.08) composites are prepared using an ultrasonic-assisted sol–gel method under a static inert atmosphere. The effects of Sn-doping on the structure and electrochemical performance of Li3V2(PO4)3/C are investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical measurements. The XRD patterns demonstrate that Sn-doping affects the preferred crystal growth direction of Li3V2(PO4)3. The SEM results show that the particles of the Sn-doped samples have a polyhedron shape. The particles are micron-size and present high crystallinity. The Li3V1.98Sn0.02(PO4)3/C sample, which has initial capacities of 122.7 and 117.2 mAh g−1 at 0.2 and 5 C between 3.0 and 4.3 V, respectively, shows the best electrochemical performance among obtained samples. During Li+ de-intercalation and intercalation processes, Sn4+ could functions as a cushion bracket to protect the Li3V2(PO4)3 crystal lattice from shrinking, which greatly improves the rate performance and cycling performance of Li3V2(PO4)3.Highlights► An ultrasonic-assisted sol–gel method is employed to prepare precursors. ► The heat treatment is processed under static inert atmosphere. ► Sn-doping affects the preferred crystal growth direction of Li3V2(PO4)3. ► The Sn-doped Li3V2−xSnx(PO4)3/C samples have a polyhedron shape. ► Doping with small amount of Sn improves electrochemical performance of Li3V2(PO4)3.

A nanostructured binary transition metal oxide, copper ferrite (CuFe2O4) is synthesized via polymer-pyrolysis method. The effects of the processing temperature on the particle size and electrochemical performance of the nanostructured CuFe2O4 are investigated. The electrochemical results show that the sample synthesized at 700 °C shows the best cycling performance, retaining a specific capacity of 551.9 mAh g− 1 beyond 100 cycles for lithium ion batteries. The electrode has a good rate capacity within the range of 0.2 C–4 C. At the highest rate of 4 C, the reversible capacity of CuFe2O4 is about 200 mAh g− 1. It is believed that the ternary transition metal oxide CuFe2O4 is quite acceptable compared with other high performance nanostructured anode materials.Highlights► A nanostructured biscuit-like CuFe2O4 is synthesized via the polymer pyrolysis method for lithium-ion batteries. ► The superior annealed temperature is 700°C. ► The obtained sample retains the reversible capacity about 551.9 mAhg−1 after 100 cycles. ► The reversible capacity is about 200 mAh g−1 at the high rate of 2C.

New applications such as hybrid electric vehicles and power backup require rechargeable batteries to combine high energy density with high charge and discharge rate capability. In this study, the core–shell Ni(OH)2@CoOOH composite is constructed via a simple cation-exchange route at moderate conditions. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) with energy dispersive X-ray (EDX), and inductively coupled plasma (ICP) are used to characterize the resulting Ni(OH)2@CoOOH composites. The Ni(OH)2@CoOOH electrode exhibits high power, higher capacity and longer life cycle when it is chosen as an positive electrode material for rechargeable alkaline MH-Ni battery. The enhanced electrochemical performance is attributed to the seamless combination of the CoOOH shell and the Ni(OH)2 core, avoiding the contact resistance between them at a large current density. It is believed that our methodology provides a simple and environment friendly route to a variety of core–shell materials with different composition and novel function.

The effects of metallic cobalt (Co) and cobalt monoxide (CoO), as additives in positive electrodes, on the electrochemical performance of nickel/metal hydride (Ni/MH) power batteries are studied. Commercial Co and CoO are charged at 50 °C in 6 M KOH solution. The oxidation mechanism of cobalt materials is investigated by observing structural and morphological evolutions during charging. A pure Co3O4-type phase is formed when the starting material is CoO. When Co is used, a cobalt oxyhydroxide (CoOOH) phase is present, together with a tricobalt tetroxide (Co3O4) phase. In both cases, the cobalt concentration in the electrolyte decreases during oxidation. The final product is dependent on the solubility of cobalt and the kinetics of the reaction that consumes cobalt tetrahydroxide [Co(OH)4]2−. The highly compact CoOOH phase, which works well between the nickel foam frame and nickel hydroxide [Ni(OH)2] particles, enhances the power performance of Ni/MH power battery. The Co3O4 phase, which works well in connecting Ni(OH)2 particles, improves the capacitive performance of Ni/MH power battery.

A nanostructured ternary transition metal oxide, ZnFe2O4, is synthesized via the simple polymer pyrolysis method. The characteristics of the material are examined by thermogravimetry, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The electrochemical test results show that this method of ZnFe2O4 synthesis produces high specific capacities and good cycling performance, with an initial specific capacity as high as 1419.6 mAh g−1 at first discharge that is maintained at over 800 mAh g−1 even after 50 charge–discharge cycles. The electrode also presents a good rate capability, with a high rate of 4C (1C = 928 mA g−1), a reversible specific capacity that can be as high as 400 mAh g−1. ZnFe2O4 is a potential alternative to high-performance nanostructured anode material in lithium ion batteries.

Spinel LiNi0.5Mn1.5O4 materials are synthesized by one-step precipitation method. Ammonium carbonate is used as the precipitating agent to obtain a more precise feed ratio without recourse to traditional washing. After annealing at high temperature, the spherical particles become angular and show high levels of crystallinity. The synthesized samples are evaluated using powder X-ray diffraction, scanning electron microscopy, and electrochemical testing. The samples synthesized with different metal ion concentrations yield different morphologies and rate performances. The sample synthesized with 0.2 mol L−1 gives the most uniform particle distribution and the best electrochemical performance. The specific discharge capacity values of the sample at 10 and 15 C are as high as 109.5 and 88.7 mAh g−1, respectively. After the high-rate cycling, its discharge capacity at 0.2 C can be reverted to 97.67% of its initial capacity.Highlights► Ammonium carbonate is used as the precipitating agent of synthesizing LiNi0.5Mn1.5O4 for the first time. ► All the metal ions precipitated in one time, no washing process is needed. ► Effect of concentration and hydrothermal on the materials are concerned. ► The obtained material shows regular quasi-spherical. ► The synthesized materials behave excellent electrochemical properties.

The activation process of Ni(OH)2 used as the positive electrode active material of Ni/MH batteries was studied by a single particle microelectrode method thanks to an improved apparatus. The images of the Ni(OH)2 particle during the charge process were collected. The electrochemical properties of Ni(OH)2 were studied by cyclic voltammetry and galvanostatic charge/discharge of a single particle. The charge efficiency (η) of the single particle was as high as 94%. The normalized output rate (NOR) was proposed as a parameter to evaluate the output performance of the electrode material. The NOR value varied with the electrode potential value. But the NOR value remained constant at fixed electrode potential value during the activation process. This implies that the activation process did not improve the reaction rate of the particle, although the capacity kept increasing during the activation process. The intrinsic nature of the activation of Ni(OH)2 was deduced as the formation of dispersed Ni(III) in the active mass. The Ni(III) phase was formed during the charge process and some remained unreduced during the discharge process. The remaining Ni(III) resulted in a much higher electronic conductivity of Ni(OH)2.Highlights► The experimental apparatus is improved. ► The color change of the single Ni(OH)2 particle can be seen during the charging and discharging process. ► The normalized output rate is proposed to evaluate the output performance of the Ni(OH)2. ► A model to describe the activation process of the single Ni(OH)2 particle is proposed.

LiMn1.5Ni0.5O4 has been synthesized by an ultrasonic-assisted sol–gel method. The precursor is heat treated at a series of temperatures from 650 °C to 1000 °C. The structure and physical–chemical properties of the as-prepared powder are investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV) thermal gravimetric and galvanostatic charge–discharge tests in detail. As temperature goes up, the particle size increases, the reactivity of the material in 4 V region becomes more obvious, the structure of the samples become more stable and it behaves optimal electrochemical properties as the material is heat treated at 850 °C. When it is used as cathode active material in a lithium battery, it delivers high initial capacity of 134.5 mAh g−1 (corresponding to 91.7% of the theoretical capacity), and high rate discharge capability, e.g., 133.4, 120.6, 111.4, 103.2 and 99.3 mAh g−1 as discharged at 0.5, 1, 5, 10 and 15 C (1 C = 148 mA g−1)-rates, respectively. It also shows satisfactory capacity retention even at high rate of 5 C, which is about 99.83% of the capacity retention per cycle.

Using an improved apparatus to investigate the activation process of single particles of hydrogen storage alloy LaNi3.55Co0.75Mn0.4Al0.3, we directly showed the particle's morphology changes during the activation process. Electrochemical properties were systematically monitored during the activation process of the single particles. We finally proposed a new parameter – normalized output rate (NOR) – to evaluate the output performance of the electrode material. In addition to revealing what occurred during the activation process, we provided a program for the quick testing of electrode materials.

The LiMnPO4/C composite material with ordered olivine structure was synthesized in 1:1(v/v) enthanol–water mixed solvent in the presence of cetyltrimethylammonium bromide (CTAB) at 240 ∘C. Rod-like particle morphology of the resulting LiMnPO4/C powder with a uniform particle dimension of 150 × 600 nm was observed by using scanning electron microscope and the amount of carbon coated on the particle surface was evaluated as 2.2wt% by thermogravimetric analysis, which is reported for the first time to date for LiMnPO4/C composite. The measurement of the electrochemical performance of the material used in rechargeable lithium ion battery shows that the LiMnPO4/C sample delivers an initial discharge capacity of 126.5 mA h g−1 at a constant current of 0.01 C, which is 74% of the theoretical value of 170 mA h g−1. The electrode shows good rated discharge capability and high electrochemical reversibility when compared with the reported results, which is verified further by the evaluation of the Li ion diffusion coefficient of 5.056×10−14 cm2/s in LiMnPO4/C.

Layered bimetal (Ni−Co/Co−Ni) hydroxide nanosheets with tunable chemical composition could be successfully constructed through a one-step partial cation exchange method by immersing Ni(OH)2/Co(OH)2 in aqueous solution of the related cobalt/nickel nitrate directly under moderate conditions. XRD, SEM, EDS, HRTEM, ICP, TGA, elemental analysis, FT-IR, and UV−vis analysis were used to identify the structure and composition of such as-prepared Ni−Co/Co-Ni hydroxide nanosheets. Enormous variants from nanostructured Ni(OH)2/Co(OH)2 could be achieved through a simple progress of one-step cation exchange. The electrochemical tests show that the as-prepared nanoscale products not only perform a larger number of exchangeable electrons (1.6e) than that of the materials with approximately the same central metal composition, which were synthesized by conventional coprecipitation method, but also exhibit lower peak oxidation potential and better reversibility. These excellent electrochemical properties could be beneficial for high-energy and high-rate power application. Moreover, the results of systemic cyclic voltammogram investigations of composition-tunable layered bimetal (Ni−Co) hydroxide nanosheets display that the trend of negative shifts of anodic current peak positions is consistent with the decrease in Nis/Cos ratios. However, there exists a range of metal ratios for keeping the electrochemical properties. Importantly, the change and maintenance of electrochemical properties with the change of metal ratios of products could provide a new way of tuning and controlling property-aimed products. In addition, this simple method can be used as an effective tool to construct nanostructures with different compositions to optimize various properties.

The effects of surface coating of Y(OH)3 on the electrochemical performance of spherical Ni(OH)2 were studied by cyclic voltammetry (CV) with soft-embedded electrode (SE-E). The coating was performed by chemical surface precipitation under different conditions. The structure, morphology, chemical composition and electrochemical properties of two different samples with surface coating of Y(OH)3 were characterized and compared. The results show that a two-step oxidation process exists in the oxidation procedure of spherical Ni(OH)2 corresponding to the formation of Ni(III) and Ni(IV), respectively. The conversion of Ni(III) to Ni(IV) is regarded as a side reaction in which Ni(IV) species is not stable. The presence of Y(OH)3 on the particle surface can restrain the side reactions, especially the formation of Ni(IV). The application of coated Ni(OH)2 to sealed Ni–MH batteries yielded a charge acceptance of about 88% at 60 °C. The results manifest that the high-temperature performance of Ni(OH)2 electrode is related to the distribution of the adding elements in surface oxide layer of Ni(OH)2, the sample with dense and porous coating surface, larger relative surface content and higher utilization ratio of yttrium is more effective.

Images of Human umbilical vein endothelial cells (HUVECs) have been obtained and the regulation of cell morphology changes after nitric oxide release has been recorded and discerned quantitatively for the first time using scanning electrochemical microscopy.

In order to understand the effect of different B-site partial substitution without the influence of calendar corrosion, the overall electrochemical performance of LaNi4.7M0.3(M=Ni,Co,Mn,Al) alloys were rapidly evaluated by means of a powder microelectrode technique (PME). The cell parameters of the alloys were also measured by XRD for a better understanding of the substitution effects. The study results show that the activation cycle is shortened by Mn partial substitution for Ni and prolonged by Co and Al partial substitution and reveal that the effect of the partial substitution of Ni improves the cycling performance in the order Co>Al>MnCo>Al>Mn and enhances the anti-electro-oxidation ability in the order MnMn>AlCo>Mn>Al, and raises the polarization of the alloy discharge reaction in the order Co>Mn>AlCo>Mn>Al. The different substitution effects mainly result from the difference in the physical properties of the substituting metals (such as Vickers hardness and atomic size) and the properties of the substituting metal oxides formed on the alloy surface.

A Li22Sn5 alloy was prepared as a novel substrate of the metallic Li anode of rechargeable Li batteries for Li+ deposition. The performance of this alloy substrate was compared with those of Li, Cu, and Sn substrates. The deposition–stripping cycling performance of Li on the substrates was studied through the galvanostatic charge–discharge method and cyclic voltammetry. The morphologies of the substrates before and after Li+ deposition were investigated through scanning electron microscopy and digital video microscopy. The electrochemical kinetics of Li+ electrodeposition on the different substrates was studied through the galvanostatic pulse method and linear sweep voltammetry. The solid electrolyte interface films of Li deposits on the substrates were characterized through electrochemical impedance spectroscopy. Results show that Li22Sn5 is an excellent substrate for metallic Li electrodes. “The competitive kinetics model” was proposed as a novel mechanistic model to explain the electrodeposition behavior of Li+ on general substrates based on electrochemical kinetic principles.